
const fp = require('lodash/fp')

// 数据
// horsepower 马力， dollar_value 价格 in_stock 库存
const cars = [
  { name: 'Ferrari FF', horsepower: 660, dollar_value: 700000, in_stock: true },
  { name: 'Spyker C12', horsepower: 650, dollar_value: 648000, in_stock: false },
  { name: 'JAGUAR xkr-s', horsepower: 550, dollar_value: 132000, in_stock: false },
  { name: 'Audi R8', horsepower: 525, dollar_value: 114200, in_stock: false },
  { name: 'Aston Martin Onr-77', horsepower: 750, dollar_value: 185000, in_stock: true },
  { name: 'Pagani Huayra', horsepower: 700, dollar_value: 130000, in_stock: false },
]

//练习1
//使用函数组合fp.flowRight()重新实现

let isLastInStock = function(cars){
  // 获取最后一条数据
  let last_car = fp.last(cars)
  // 获取最后一条数据的 in_stock 属性值
  return fp.prop('in_stock', last_car)
}

let isLastInStockFp = fp.flowRight(fp.prop('in_stock'), fp.last)

console.log(isLastInStock(cars))
console.log(isLastInStockFp(cars))



//练习2
//使用fp.flowRight()、fp.prop()和fp.first()获取第一个car的name

let getFirstCarName = fp.flowRight(fp.prop('name'), fp.first)
console.log(getFirstCarName(cars))




//练习3
//使用帮助函数_average重构averageDollarValue，使用函数组合的方式实现
let _average = function(xs) {
  return fp.reduce(fp.add, 0, xs) / xs.length
} // <-无须改动


let averageDollarValue = function (cars){
  let dollar_values = fp.map(function(car){
    return car.dollar_value
  }, cars)
  return _average(dollar_values)
}


let averageDollarValueFp = fp.flowRight(_average, fp.map(car => car.dollar_value))
console.log(averageDollarValue(cars))
console.log(averageDollarValueFp(cars))



//练习4
//使用flowRight写一个sanitizeNames()函数，返回一个下划线连接的小写字符串，把数组中的name转换为这种形式：例如：sanitizeNames(["Hello World"])=>["hello_world"]
let _underscore = fp.replace(/\W+/g, '_') //无须改动，并在sanitizeNames中使用它
const sanitizeNames = fp.map(fp.flowRight(fp.toLower, _underscore))
console.log(sanitizeNames(["Hello World"]))